Keep in mind that there are two types of Oxygen Sensor,
narrow band 0.1 to 1.0 volts
and
Wide Band 0.1 to 5 volts.
https://en.wikipedia.org/wiki/Oxygen_sensorIf you have a small gasoline engine powered device like a lawn mower or electric generator
you can make a test device by making a pipe section with a threaded side hole for the Oxygen sensor.
Slip this pipe over the muffler outlet and let the exhaust flow through past the Oxygen sensor.
With the engine running normally the Oxygen sensor should read slightly lean, engage the Choke on the engine and it should read rich.
You can actually use this same test device to check the correct running of your natural gas furnace.
Most Oxygen sensors will go bad if you get metal deposits on their CeO2 ceramic,
such as Zinc from burning lubricating oil in the cylinder,
or Lead from running Tetra-Ethyl leaded gasoline, such as Aviation or Race gasoline.
